First, domain mode != clustering, they are two different concepts.
Domain is the ability to manage all instance from a single point called domain controller, but it can or not be configured as HA.
To have HA you should use -ha.xml profiles.
Hope this helps.
Thanks for your reply..
We are aware of that we were trying in both ways domain as well as standalone and we were able to achieve HA at server Level.
Problem comes when we try to achieve through portlet container.
We downloaded jpp-6.1 which is having portlet container bundled with jboss eap.
which gives exception as i have listed on rhel.
Could you please help there?